The Hindu , 03 January 2006

Tsunami alert by Australia defended

VISAKHAPATNAM, JAN. 1. As many as 51 earthquakes of moderate and major intensity were recorded near the Andaman and Nicobar Islands and Sumatra islands since Sunday's earthquake which caused tsunami and massive destruction.

While 17 earthquakes were recorded near the Andaman islands, 14 were near the Nicobar islands and 20 near Sumatra islands, the Director of the Cyclone Warning Centre (CWC), J.V.M. Naidu, said in a chat with The Hindu .

The intensity of these earthquakes recorded on the Richter scale was between 5.2 and 7.3.

(An earthquake is called as moderate if it is of intensity between five to 6.9 on the Richter scale, major if its is between seven and 7.9 and as great if it is above eight).

The one recorded near Sumatra islands at 9.57 a.m. on Friday is of 5.3 intensity on the Richter scale.

This was noticed by the Australian authorities who sounded an alert of the likelihood of some more earthquakes along with tsunami, to all the countries that were linked in the existing tsunami alert system.

The same alert was noticed by the Government of India which in turn alerted all its coastal regions. There was a possibility of the Indian coast being affected if an earthquake occurred below the Sumatra islands and near Australia, he said.

Dr. Naidu said that the alert by the Australians must have been made after considering several parameters. An earthquake and tsunami might or might not be possible but an alert was good.

Precautionary action

It was not possible to take full-scale precautionary action after a tsunami was noticed since there would not be much time left before it hit the coast (it took about half-an-hour for it to reach the Andaman islands and about two hours for some coastal areas of main land on Sunday).

Hence, as the first and immediate precaution, it was advisable for people living on the coastal areas susceptible to a tsunami strike, to leave for safer places as soon as they noticed signs of an impending earthquake such as rattling of household articles, doors and windows and things falling from the shelves, Dr. Naidu said.

For people living in Visakhapatnam, which is located on an elevated place, it was sufficient if they moved about 500 metres away from the coast.

In other places like Krishna and Prakasam, people should move about 1 km.

On some methods being followed to monitor and predict an earthquake in the ocean bed and the resultant tsunami, Dr. Naidu said that borewells to a depth of 1 to 2 km were dug in susceptible areas.

Gas monitoring

The radon gas was monitored in these borewells since this gas would be released a couple of days before an earthquake occurred.

Watching the water levels in the neighbourhood of the susceptible areas and watching temperature through remote sensing were some of the other measures.